Flood hydrologic response is influenced by rainfall structure (i.e., variability in space and time). How this structure shapes flood frequency is unknown, and flood frequency analyses typically ...neglect or simplify potentially important aspects of rainfall variability. This study seeks to understand how rainfall structure impacts flood frequency. We use stochastic storm transposition combined with a 15‐year record of hourly, 4‐km2 radar rainfall to generate 10,000 synthetic extreme rain events. These events are resampled into four “scenarios” with differing spatial and temporal resolutions, which are used as input to a distributed hydrologic model. Analysis of variance is used to identify the proportions of total flood peak variability attributable to spatial and to temporal rainfall variability under two antecedent soil moisture conditions. We simulate peak discharges for recurrence intervals of 2 to 500 years for 1,343 subwatersheds ranging in size from 16 to 4,400 km2 in Turkey River in the Midwestern United States, which is situated in a typically humid continental climactic region. Antecedent soil moisture modulates the role of rainfall structure in simulated flood response, particularly for more frequent events and large watershed scales. Rainfall spatial structure is more important than temporal structure for drainage areas larger than approximately 2,000 km2 (approximately 200 km2) for wet (dry) initial soil conditions, especially when soils are dry, while the reverse is true for smaller subwatersheds. The results appear to be related to the differing propensities for surface and subsurface runoff production as a function of basin scale, event magnitude, and soil saturation. Our results suggest that hydrologic model‐based flood frequency analyses, and particularly efforts attempting to spanning a range of scales, must carefully consider rainfall structure.
Plain Language Summary
There is increasing interest in “derived flood frequency analysis”: the use of stochastically generated rainfall and high‐resolution distributed hydrologic models to understand current and future flood frequency. Potential issues surrounding rainfall structure, resolution, and accuracy in this context have received very little attention, however. Design storm methods, common in hydrologic engineering practice, use highly idealized assumptions regarding rainfall space‐time structure, and the consequences of these assumptions are poorly understood. This study seeks to better understand how flood frequency is affected by rainfall spatial and temporal structure, as well as how these effects are modulated by watershed initial conditions (i.e., antecedent soil moisture). The findings, which are summarized in the manuscript's , should be useful for future researchers and practitioners. We believe that this work constitutes a useful contribution in the effort to advance the derived flood frequency analysis.
Key Points
Framework for partitioning impacts of rainfall spatial and temporal variability on flood frequency
The impact of rainfall structure varies significantly with antecedent soil moisture, watershed scale, and event magnitude
Rainfall temporal variability is more important than spatial variability at small scales; the opposite is true at large scales
Every year in early August, a breeze borne by silent messengers from another time blows through Iowa. It carries a whiff of something wonderful, something far off and a bit unclear, yet oddly ...familiar. It's a reminder that an extraordinary annual event is about to take place, just as it has for more than 150 years: the Iowa State Fair.In 2013, Kurt Ullrich set out to chronicle the magic of the Iowa State Fair in words and photographs. Join him as August days and nights blow warm and easy over the fairgrounds, brushing lightly against fellow travelers on this earth, both human and not. He captures precious moments of extreme joy and unbridled delight in these beautiful black-and-white images, celebrating the brash rural energy of the fair, from Big Wheel races to people-watching goats, fair queen contestants to arm wrestlers, Percherons to ponies. Prize pigs, prize sheep, prize apples, and the famous butter cow all have their moment in the limelight. Iowa's very best ear of corn and old friends reminiscing outside their RVs draw the photographer's fond eye, as do brightly lit beer stands and the brilliant arc of the Ferris wheel against the night sky.If you always go to the Iowa State Fair, this book is for you. If you've never been, it will show you what you're missing-and you'll understand why it's well past time you dropped by.
The execution of hydraulic models at large spatial scales has yielded a step change in our understanding of flood risk. Yet their necessary simplification through the use of coarsened terrain data ...results in an artificially smooth digital elevation model with diminished representation of flood defense structures. Current approaches in dealing with this, if anything is done at all, involve either employing incomplete inventories of flood defense information or making largely unsubstantiated assumptions about defense locations and standards based on socioeconomic data. Here, we introduce a novel solution for application at scale. The geomorphometric characteristics of defense structures are sampled, and these are fed into a probabilistic algorithm to identify hydraulically relevant features in the source digital elevation model. The elevation of these features is then preserved during the grid coarsening process. The method was shown to compare favorably to surveyed U.S. levee crest heights. When incorporated into a continental‐scale hydrodynamic model based on LISFLOOD‐FP and compared to local flood models in Iowa (USA), median correspondence was 69% for high‐frequency floods and 80% for low‐frequency floods, approaching the error inherent in quantifying extreme flows. However, improvements versus a model with no defenses were muted, and risk‐based deviations between the local and continental models were large. When simulating an event on the Po River (Italy), built and tested with higher quality data, the method outperformed both undefended and even engineering‐grade models. As such, particularly when employed alongside model components of commensurate quality, the method here generates improved‐accuracy simulations of flood inundation.
Plain Language Summary
Traditional flood risk assessments are carried out using computer models built with local data, but their spatial coverage is impaired by how expensive and time‐consuming they are to produce. Recent advances in data availability, understanding of necessary physical process representation, and computational capacity have enabled hydraulic models of the entire globe to be built in an automated fashion at a fraction of the financial and human cost. However, their accuracy can be significantly impaired by a lack of information on flood defenses. As the model is built, elevation data are coarsened to reduce the number of calculations required to simulate flooding over such wide areas. This results in flood defense structures being smoothed out of the terrain information used in the model. Publicly available defense inventories are of insufficient coverage to ameliorate this issue. In this paper, a method is presented, which automatically detects levee‐like features in high‐resolution elevation data and accurately represents their heights during this necessary coarsening process. Simulating flood inundation over this “defended” topography results in high correspondence between local models and observations for test cases in the United States and Italy, with improvements particularly felt where a lack of defense information is the dominant source of error.
Key Points
Flood defense representation is presently poor in large‐scale flood models, impairing their ability to map flood hazard accurately
A new method is presented, which automatically identifies hydraulic structures in terrain data and accurately preserves their elevations
Hydraulic simulations where a lack of defense data is the dominant error show significant improvements in skill when incorporating this method
Two sites near the eastern margin of the Cretaceous Western Interior Sea (WIS) were investigated. The section at Cuba, Kansas (CK) is ~630km east of the GSSP for the Cenomanian/Turonian boundary at ...Rock Canyon, Colorado (RC), and the section near Sioux City, Iowa (SCI) is ~315km northeast of the Cuba site. Surprisingly, planktic foraminifera dominate all the studied samples despite the relative proximity of the sites to the paleo-shoreline and presumed neritic water depths. Such dominance suggests inhospitable benthic environments, and benthic foraminiferal assemblages indicate that seafloor oxygen in the WIS decreased eastward. Therefore, the hypothesis of an influx of freshwater into the WIS from the western margin forming a fresh water cap that diminished eastward is not supported. Benthic foraminifera are scarce in most studied samples and species diversity is low. In the CK section, diversity and abundance increase abruptly in the uppermost Cenomanian Benthonic Zone at the initiation of the δ13Corg positive excursion marking the onset of Oceanic Anoxic Event (OAE 2). In the SCI section, however, the Benthonic Zone is recognized only by presence of Nodosaria bighornensis that has a stratigraphic range restricted to this interval; other benthic taxa are very rare or absent. The favorable conditions of the Benthonic Zone were short-lived. While relatively diverse planktic foraminiferal assemblages, including keeled species, characterize the initial δ13C excursion at the CK site, dwarfed specimens of Heterohelix and Hedbergella dominate the assemblages at the more proximal Sioux City site. Furthermore, most of the biostratigraphic events recognized in the basin center RC section can be traced into the CK section, but not into the SCI section, including the Rotalipora spp. and Globigerinelloides bentonensis extinctions, the Heterohelix shift event, and the brief benthic recovery event. Correlation between eastern WIS sites shows that the SCI section is thicker, suggesting a major sediment source to the east. This may explain the inhospitable benthic conditions and development of a ‘dead zone’ (seasonal hypoxia) analogous to the modern shelf of the northern Gulf of Mexico proximal to active discharge of the Mississippi River. Development of estuarine circulation in the WIS provided the eastern part of the basin with input of calcareous plankton from the south including planktic foraminifera. Foraminiferal assemblages, total organic carbon (TOC), and δ13C data of the studied sections suggest a two-fold history of Greenhorn transgression and OAE 2 development. The initial phase is a global signal characterized by a positive δ13C excursion, low TOC values, and high foraminiferal species diversity. The second phase is characterized by overprinting by local conditions in the WIS, including high fluvial input, relatively high TOC values, and low foraminiferal species diversity. These findings suggest that the eastern margin records unique depositional and biotic environments further revealing the dynamic and complex nature of the WIS and its sedimentary cycles.
•We suggest that the eastern side of the seaway was a major source of sediments.•A dead zone was developed along the eastern margin due to upwelling.•Eastern and central parts of the WIS were under the influence of same watermass.•A strong gyre drifted keeled species into the eastern part of the basin.
As Americans geared up for World War II, each state responded according to its economy and circumstances—as well as the disposition of its citizens. This book considers the war years in Iowa by ...looking at activity on different home fronts and analyzing the resilience of Iowans in answering the call to support the war effort. With its location in the center of the country, far from potentially threatened coasts, Iowa was also the center of American isolationism—historically Republican and resistant to involvement in another European war. Yet Iowans were quick to step up, and Lisa Ossian draws on historical archives as well as on artifacts of popular culture to record the rhetoric and emotion of their support. Ossian shows how Iowans quickly moved from skepticism to overwhelming enthusiasm for the war and answered the call on four fronts: farms, factories, communities, and kitchens. Iowa's farmers faced labor and machinery shortages, yet produced record amounts of crops and animals—even at the expense of valuable topsoil. Ordnance plants turned out bombs and machine gun bullets. Meanwhile, communities supported war bond and scrap drives, while housewives coped with rationing, raised Victory gardens, and turned to home canning. The Home Fronts of Iowa, 1939–1945 depicts real people and their concerns, showing the price paid in physical and mental exhaustion and notes the heavy toll exacted on Iowa's sons who fell in battle. Ossian also considers the relevance of such issues as race, class, and gender—particularly the role of women on the home front and the recruitment of both women and blacks for factory work—taking into account a prevalent suspicion of ethnic groups by the state's largely homogeneous population. The fact that Iowans could become loyal citizen soldiers—forming an Industrial and Defense Commission even before Pearl Harbor—speaks not only to the patriotism of these sturdy midwesterners but also to the overall resilience of Americans. In unraveling how Iowans could so overwhelmingly support the war, Ossian digs deep into history to show us the power of emotion—and to help us better understand why World War II is consistently remembered as "the Good War."
Land management affects soil structure and many other soil properties and processes. Our objectives were to evaluate soil organic C (SOC), aggregate size distribution, aggregate‐associated C, and ...soil structure as affected by long‐term land management and slope. A chronosequence of 38 on‐farm sites with low to high (5–18%) slopes was selected to evaluate 5–40 yr of management. The sites were classified as business as usual (BAU) cropland (BAU‐Crop), BAU pasture (BAU‐Past), newly established conservation reserve program (CRP) areas (CRP‐New), and established CRP (CRP‐Old). Soil samples were collected from the 0‐to‐5‐ and 5‐to‐15‐cm depth increments and processed for soil property measurements including fractionation by wet sieving into five aggregate size classes (>2,000, 1,000–2,000, 500–1,000, 250–500, and 53–250 μm). Within the surface 5 cm, mean weight diameter (MWD) and geometric mean diameter (GMD) were used to characterize soil structural stability. The BAU‐Past and CRP‐Old sites had 79% more macroaggregates (>2,000, 1,000–2,000, and 500–1,000 μm), 123% higher MWD, 38% higher GMD, and 47% higher SOC than BAU‐Crop or CRP‐New sites. The 5‐to‐15‐cm depth increment showed a similar but lower magnitude response. Aggregate‐associated C was quantified using a constant soil mass that reflected aggregate size distribution to prevent overestimating C content. Lower‐slope locations had more SOC, more macroaggregates, more C associated with macroaggregates, and higher GMD and MWD compared with high‐slope locations across all management classifications and soil depths. The results support our hypothesis that the high‐slop soils may benefits from specific management decisions than the lower‐sloping soils as a function of landscape property. We recommend reestablishing grassland on sloping land that is susceptible to excessive soil erosion, although those practices will likely take a long time to restore soil structural stability and SOC content to precultivation levels.
Core Ideas
Land management significantly affected soil structural stability and C dynamics.
Cropland was characterized more by microaggregates than macroaggregates.
Higher slopes had lower soil structural stability and soil organic C (SOC) than lower slopes.
SOC should be measured using a constant mass representing aggregate size distribution.
Restoring soil stability to the prairie level will take 10–40 yr or more.
Hydroclimatic stationarity is increasingly questioned as a default assumption in flood risk management (FRM), but successor methods are not yet established. Some potential successors depend on ...estimates of future flood quantiles, but methods for estimating future design storms are subject to high levels of uncertainty. Here we apply a Nonstationary Decision Model (NDM) to flood risk planning within the decision scaling framework. The NDM combines a nonstationary probability distribution of annual peak flow with optimal selection of flood management alternatives using robustness measures. The NDM incorporates structural and nonstructural FRM interventions and valuation of flows supporting ecosystem services to calculate expected cost of a given FRM strategy. A search for the minimum‐cost strategy under incrementally varied representative scenarios extending across the plausible range of flood trend and value of the natural flow regime discovers candidate FRM strategies that are evaluated and compared through a decision scaling analysis (DSA). The DSA selects a management strategy that is optimal or close to optimal across the broadest range of scenarios or across the set of scenarios deemed most likely to occur according to estimates of future flood hazard. We illustrate the decision framework using a stylized example flood management decision based on the Iowa City flood management system, which has experienced recent unprecedented high flow episodes. The DSA indicates a preference for combining infrastructural and nonstructural adaptation measures to manage flood risk and makes clear that options‐based approaches cannot be assumed to be “no” or “low regret.”
Key Points:
An innovative decision analytic flood risk management model for nonstationary probability distribution of extreme flows
Model reveals performance of flood management alternatives under uncertain future flood hazard and environmental flow value
Case study reveals nonstructural alternative, typically described as “no regret” is high‐regret for increasing trends in flood hazard
Alzheimer's disease (AD) is the most common form of neurodegenerative diseases, characterized by the deposition of Aβ (amyloid beta) peptide. In this study, we have unravelled the interactions as ...well as anti amyloidogenic behaviour of 40 small molecule inhibitors with Aβ
peptide and Iowa mutant D
N-Aβ1
peptide at atomic level and their modes of binding by docking approaches. The binding mode between wild type peptide and drug is distinctly different from the Iowa-mutant-peptide and drug. Here we proposed possible mechanisms of amyloid beta peptide inhibition by small molecule and prevent monomer-monomer interactions via at least three different mechanisms. In the first mechanism, four catechins efficiently interacted with the C-terminal region of peptides through hydrogen bonds and inhibited the peptides. This may lead to blockage of access of second molecule of Aβ-peptide. Secondly, in the case Iowa mutant D23N-Aβ
peptide, same catechin form hydrogen bond with the important mutated Asn
residue which acts as hydrogen bond donor and acceptor leading to tight binding of inhibitor with the peptide and may prevent monomer-monomer interactions. The third mechanism relies on the ability of drug molecules to mask hydrophobic residues of the peptide, thereby possibly inhibiting hydrophobic interactions between the two beta peptides.
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